Newsletter—November 2010

Archives

Recent Advisory News

Alabama issues 2010 fish advisories

The Alabama Department of Public Health (ADPH) recently released updated fish consumption advisories based on data collected in the fall of 2009 by the Alabama Department of Environmental Management (ADEM). Beginning with the 2007 advisories, ADPH adopted a contaminant level for mercury in fish based on U.S. Environmental Protection Agency (EPA) standards that would better protect those who might consider eating more than one fish meal per week. New consumption advisories were issued for the 17 bodies of water in 2010, and all advisories previously issued using U.S. Food and Drug Administration (FDA) guidelines remain in effect for 2010. Other advisories have been updated to reflect the EPA consumption levels for mercury contaminated fish.

Source: WKRG.com News (AL), 10/7/2010

Algal bloom leads to warning on fish consumption

The Kitsap County Health District (Washington State) issued a public health advisory about a highly toxic blue-green algae bloom in Kitsap Lake. Preliminary analysis of a water sample taken at the lake showed high levels of toxins, which, if ingested in sufficient quantities, can make people sick. While the advisory is in effect, people should avoid drinking water from the lake; swimming in the lake; eating fish caught from the lake; and allowing pets and livestock access to the lake.

Source: Kitsap Sun (WA), 9/17/2010

South Carolina: No mercury warnings for Lake Murray

While mercury has shown up in bass from Lake Murray for at least the past decade, the lake remains one of the few major waterbodies, from the Midlands to the coast, that does not carry an advisory against eating more than moderate amounts of some fish species. State officials said the amounts of mercury in Lake Murray fish based on a 3-year average remain below the limit used in deciding whether to issue warnings, which is 0.25 parts per million. Jim Glover at the S.C. Department of Health and Environmental Control suggests that mercury in Lake Murray fish has been influenced, in part, by decisions to raise and lower the lake’s water level for various reasons over the past decade, a factor that sometimes can increase mercury levels.

Recent Research

Mercury concentrations in three brands of canned tuna

This study was conducted to examine the amount of mercury present in three different brands of canned tuna. One brand had significantly more mercury than the other two, and 55% of all tuna tested was above the EPA safety level for human consumption (0.5 ppm). In addition, 5% of the tuna exceeded the action level established by the FDA (1.0 ppm). Based on these results and according to the EPA reference dose of 0.1 microg/kg body weight per day and a mean mercury value of 0.619 ppm, a 25-kg child may consume one meal (75 g) of canned chunk white tuna only once every 18.6 days.

PCBs and pesticides in fish from the Aleutian Islands of Alaska

This study examined the levels of polychlorinated biphenyls (PCBs) and three pesticides [p, p'-DDE, mirex, and hexachlorobenzene (HCB)] in muscle tissue from nine fish species from several locations around the Aleutian Islands of Alaska. The highest median PCB level was found in rock sole, while the lowest level was found in rock greenling. Among the pesticides, p, p'-DDE was the most prevalent, and the highest level was found in sockeye salmon. Based on EPA methods for cancer health endpoints, all species would trigger strict advisories of between two and six meals per year for PCBs. For noncancer effects by PCBs, advisories of between 7 and 22 meals per year would be triggered. None of the pesticides would trigger consumption limits. The authors note that the many health and cultural benefits of eating fish must also be considered when assessing any risk of the Alaska native traditional diet.

Analysis of fish tissue mercury in South Carolina, 1993–2007

The South Carolina Department of Health and Environmental Control analyzed fish tissue mercury (skin-on-filet) data from 1993 to 2007 to determine biotic, spatial, and temporal trends in tissue mercury levels in South Carolina. The researchers found that the large pelagic, piscivorous fish species, such as bowfin, had higher levels of tissue mercury than smaller omnivorous species. Habitat was also an important indicator—estuarine species had lower levels of tissue mercury than freshwater species, fish from small reservoirs had higher levels of tissue mercury than those from large reservoirs, and fish from areas with more wetlands also had higher levels of tissue mercury. The authors found that fish tissue mercury levels have trended lower from 1993–2007, with a spike in 2003–2005 that may have been cause by the drying and rewetting of the landscape after the 2002 drought.

Trends in fish tissue mercury in Louisiana, 1994–2008

The authors analyzed data from Louisiana’s fish tissue mercury database, which includes 15 years of data collected from 368 waterbodies. The analysis showed that the mean fish tissue mercury level was 0.218 ppm and that 44% of all samples had mercury levels above EPA's criterion of 0.3ppm. Species of potential concern include cobia, king mackerel, blackfin tuna, greater amberjack, spotted bass, bowfin, largemouth bass, and freshwater drum. The analysis also found that largemouth bass mercury levels in Louisiana experienced a slight but statistically significant decline from 1994–1999 to 2003–2008.

Fish consumption behaviors during pregnancy

The researchers conducted focus groups with pregnant women from the Boston area to study their behaviors regarding fish consumption. Results showed that many women had received advice to limit the amount of fish they ate due to mercury contamination. None of the women had been advised to eat fish. While some women knew that fish contains the beneficial omega-3 fatty acid docosahexaenoic acid (DHA), most had not received information about which fish types contain more DHA or less mercury. The authors suggest that if physicians advised eating fish or if a reference regarding which fish are safe to eat was provided, pregnant women might be willing to eat more fish.

Mercury exposure and scholastic achievement in the Seychelles Child Development Study

The authors undertook an assessment of school success of children in the Seychelles Child Development Study main cohort to determine if there were any associations with either prenatal or recent postnatal methylmercury exposure. The primary endpoints were Seychelles nationally standardized end-of-year examinations given when the cohort children were 9 and 17 years of age. A subgroup from the main cohort was also examined at 9 years of age using a regional achievement test called SACMEQ. Multiple linear regression analyses showed no pattern of associations between prenatal or postnatal exposure, and either the 9- or 17-year end-of-year examination scores. For the subgroup of 215 subjects who participated in the SACMEQ test, there were significant adverse associations between examination scores and postnatal exposure, but only for males. The average postnatal exposure level in child hair for this subgroup was significantly higher than for the overall cohort. The authors conclude that these results are consistent with their earlier studies and support the interpretation that prenatal methylmercury exposure at dosages achieved by mothers consuming a diet high in fish are not associated with adverse educational measures of scholastic achievement. The adverse association of educational measures with postnatal exposure in males is intriguing, but will need to be confirmed by further studies examining factors that influence scholastic achievement.

Toxic metals in seafood sold in New York State

Concentrations of several metals were determined in samples of fish and lobster obtained from various stores and markets in New York State. Twenty-two samples had mercury concentrations greater than the limit of 1,000 nanograms per gram set by the Commission of the European Communities. All levels of arsenic, cadmium, chromium, lead, and nickel were below the FDA action levels for these metals in crustaceans and shellfish. The highest average mercury level was found in swordfish. The highest average arsenic level was found in monkfish.

King, T.J., R.S. Sheridan, and D. H. Rice. (2010). Analysis of toxic metals in seafood sold in New York State by inductively coupled plasma mass spectrometry and direct combustion analysis. Journal of Food Protection 73(9).

Does proximity to coal-fired power plants influence fish tissue mercury?

In this study, the authors quantified the relative importance of proximity to coal-fired power plants on mercury accumulation in two fish species of different trophic positions. Fish, water and sediment were collected and analyzed from 14 lakes, seven near (less than 10 kilometers) to and seven far (more than 30 kilometers) from coal-fired power plants. Lower tissue mercury and higher tissue selenium concentrations were measured in fish collected near power plants. Moreover, mercury accumulation in fish was driven by biotic characteristics (e.g., trophic position, total length, age), waterbody characteristics (e.g., pH, dissolved organic carbon and sulfate) and distance from power plants. The authors conclude that proximity to an atmospheric point-source of mercury and selenium, such as a coal-fired power plant, affects the quantities of mercury and selenium accumulated in fish tissue. Differences in accumulation are hypothesized to be driven in part by selenium-mitigated reductions in fish tissue mercury near power plants. Although reduced fish tissue mercury in systems near power plants may decrease mercury-specific risks to human consumers, these benefits are highly localized and the relatively high selenium associated with these tissues may compromise ecological health.

The South Carolina Department of Health and Environmental Control collected tissue data in Lake Murray before and after several unique events between 2003–2005, including the drawdown of lake water levels for dam construction, the introduction of sterile grass carp, and a period of higher precipitation after several years of drought. Two sites were monitored annually over this period, one close to and one further away from the dam site. In 2004, tissue mercury in largemouth bass at the far site was elevated relative to previous years, while at the site close to the dam, levels were depressed. In 2005, tissue mercury levels fell at the close site, while they were found to increase at the far site. The authors suggest that many differences between the two sites likely contributed to these patterns in fish tissue mercury levels over the study period.

Glover, J.B., and K.C. Altman. 2010. Factors contributing to the temporal trends in tissue mercury levels in largemouth bass from Lake Murray (South Carolina, USA). Proceedings of the 2010 South Carolina Water Resources Conference, held October 13-14, 2010, at the Columbia Metropolitan Convention Center.